Electric motors (e.g., DC electric motors) have a rotating motor portion (“rotor”) that rotates in response to a magnetic field produced by a stationary motor portion (“stator”). Stated another way, the magnetic field produced by the stator causes the rotor to rotate about an axis formed by a rotor shaft that is rotatably secured to the stator. To produce the magnetic field, the stator typically includes a metallic stator core made up of a plurality of stacked metal laminations, a coil wrapped around the stator core, and a circuit board for selectively energizing the coil. Circuit elements on the circuit board thus detect the magnetic field produced by a magnet on the rotor, and selectively energize the coil to provide rotating energy to the rotor.
Rotors often rotate at relatively high rates, such as six thousand revolutions per minute and higher. When rotating at such high rates, it is important that the rotor be properly balanced to ensure that it rotates without significantly vibrating. Among other disadvantages, vibrations can cause the motor to malfunction, and can reduce the lifetime and efficiency of the motor. A motor generally is considered to be balanced when the axis of its shaft is substantially coaxially aligned with the effective axis of the remainder of the rotor. This alignment typically ensures that the rotor smoothly rotates about its axis with negligible vibration.
Shafts commonly are connected to the remainder of the rotor during a mechanical or manual assembly process. Such processes, however, commonly misalign the shaft with the axis of the remainder of the rotor. For example, the shaft may not be perpendicularly connected to the remainder of the rotor, and/or the axis of the remainder of the rotor may not be coincident with the axis of the shaft. Consequently, additional processes are required to both test each produced rotor, and make adjustments to the weighting of the rotor when a tested rotor is determined to be improperly balanced. In addition to increasing manufacturing costs, this process is prone to error.